Gator Engineering 1 Chapter 2 C Fundamentals (Continued) Copyright © 2008 W. W. Norton & Company. All rights reserved.

Gator Engineering Programming Exercises

Gator Engineering Programming Exercises 2.1 3

Gator Engineering Programming Exercises 2.4 4

Gator Engineering Programming Exercises 2.5 5

Gator Engineering Defining Names for Constants dweight.c and dweight2.c rely on the constant 166, whose meaning may not be clear to someone reading the program. Using a feature known as macro definition, we can name this constant: #define INCHES_PER_POUND 166 6

Gator Engineering Defining Names for Constants When a program is compiled, the preprocessor replaces each macro by the value that it represents. During preprocessing, the statement weight = (volume + INCHES_PER_POUND - 1) / INCHES_PER_POUND; will become weight = (volume ) / 166; Non-changeable Once and for all Easier understanding Rules 7

Gator Engineering Defining Names for Constants The value of a macro can be an expression: #define RECIPROCAL_OF_PI (1.0f / f) If it contains operators, the expression should be enclosed in parentheses. Using only upper-case letters in macro names is a common convention. 8

Gator Engineering Program: Converting from Fahrenheit to Celsius The celsius.c program prompts the user to enter a Fahrenheit temperature; it then prints the equivalent Celsius temperature. Sample program output: Enter Fahrenheit temperature: 212 Celsius equivalent: The program will allow temperatures that aren’t integers. The conversion formulas between °F and °C are: [°C] = ([°F] - 32) × 5/9 [°F] = [°C] × 9/

Gator Engineering celsius.c /* Converts a Fahrenheit temperature to Celsius */ #include #define FREEZING_PT 32.0f #define SCALE_FACTOR (5.0f / 9.0f) int main(void) { float fahrenheit, celsius; printf("Enter Fahrenheit temperature: "); scanf("%f", &fahrenheit); celsius = (fahrenheit - FREEZING_PT) * SCALE_FACTOR; printf("Celsius equivalent: %.1f\n", celsius); return 0; } 10

Gator Engineering Program: Converting from Fahrenheit to Celsius Defining SCALE_FACTOR to be (5.0f / 9.0f) instead of (5 / 9) is important. Note the use of %.1f to display celsius with just one digit after the decimal point. 11

Gator Engineering Identifiers Names for variables, functions, macros, and other entities are called identifiers. An identifier may contain letters, digits, and underscores, but must begin with a letter or underscore: times10 get_next_char _done It’s usually best to avoid identifiers that begin with an underscore. Examples of illegal identifiers: 10times get-next-char 12

Gator Engineering Identifiers C is case-sensitive: it distinguishes between upper-case and lower-case letters in identifiers. For example, the following identifiers are all different: job joB jOb jOB Job JoB JOb JOB 13

Gator Engineering Identifiers Many programmers use only lower-case letters in identifiers (other than macros), with underscores inserted for legibility: symbol_table current_page name_and_address Other programmers use an upper-case letter to begin each word within an identifier: symbolTable currentPage nameAndAddress C places no limit on the maximum length of an identifier. 14

Gator Engineering Programming guildlines Pascal case –Function, e.g. PrintMyName() –Global variables, e.g. int GlobalCounter Camel case –Local variables, e.g. int volume = 10 –Parameters, e.g. Add(int val1, int val2) 15

Gator Engineering Keywords The following keywords can’t be used as identifiers: auto enum restrict* unsigned break extern return void case float short volatile char for signed while const goto sizeof _Bool* continue if static _Complex* default inline* struct _Imaginary* do int switch double long typedef else register union *C99 only 16